Flash memory device with data output control

ABSTRACT

An apparatus, system, and computer-implemented method for controlling data transfer between a plurality of serial data link interfaces and a plurality of memory banks in a semiconductor memory is disclosed. In one example, a flash memory device with multiple links and memory banks, where the links are independent of the banks, is disclosed. The flash memory devices may be cascaded in a daisy-chain configuration using echo signal lines to serially communicate between memory devices. In addition, a virtual multiple link configuration is described wherein a single link is used to emulate multiple links.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.11/324,023 entitled “Multiple Independent Serial Link Memory” filed onDec. 30, 2005, which claims the benefit of priority from U.S.Provisional Application No. 60/722,368 entitled “Multiple IndependentLink Serial Memory” filed Sep. 30, 2005, the disclosure of which isexpressly incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The invention relates to semiconductor memory devices. Moreparticularly, the invention relates to a memory architecture forimproving the speed and/or capacity of semiconductor Flash memorydevices.

BACKGROUND OF THE INVENTION

Mobile electronic devices, such as digital cameras, portable digitalassistants, portable audio/video players and mobile terminals continueto require mass storage memory, preferably non-volatile memory with everincreasing capacities and speed capabilities. For example, presentlyavailable audio players can have between 256 Mbytes to 40 Gigabytes ofmemory for storing audio/video data. Non-volatile memory such as Flashmemory and hard-disk drives are preferred since data is retained in theabsence of power, thus extending battery life.

Presently, hard disk drives have high densities and can store 20 to 40Gigabytes of data, but are relatively bulky. However, Flash memory, alsoknown as a solid-state drive, is popular because of their high density,non-volatility, and small size relative to hard disk drives. The adventof multi-level cells (MLC) further increases the Flash memory densityfor a given area relative to single level cells. Those of skill in theart will understand that Flash memory can be configured as NOR Flash orNAND Flash, with NAND Flash having higher density per given area due toits more compact memory array structure. For the purposes of furtherdiscussion, references to Flash memory should be understood as beingeither NOR or NAND type Flash memory.

While existing Flash memory modules operate at speeds sufficient formany current consumer electronic devices, such memory modules likelywill not be adequate for use in future devices where high data rates aredesired. For example, a mobile multimedia device that records highdefinition moving pictures is likely to require a memory module with aprogramming throughput of at least 10 MB/s, which is not obtainable withcurrent Flash memory technology with typical programming data rates of 7MB/s. Multi-level cell Flash has a much slower rate of 1.5 MB/s due tothe multi-step programming sequence required to program the cells.

Programming and read throughput for Flash memory can be directlyincreased by increasing the operating frequency of the Flash memory. Forexample, the present operating frequency of about 20-30 MHz can beincreased by an order of magnitude to about 200 MHz. While this solutionappears to be straightforward, there is a significant problem withsignal quality at such high frequencies, which sets a practicallimitation on the operating frequency of the Flash memory. Inparticular, the Flash memory communicates with other components using aset of parallel input/output (I/O) pins, numbering 8 or 16 depending onthe desired configuration, which receive command instructions, receiveinput data and provide output data. This is commonly known as a parallelinterface. High speed operation will cause well known communicationdegrading effects such as cross-talk, signal skew and signalattenuation, for example, which degrades signal quality.

Such parallel interfaces use a large number of pins to read and writedata. As the number of input pins and wires increases, so do a number ofundesired effects. These effects include inter-symbol interference,signal skew and cross talk. Inter-symbol interference results from theattenuation of signals traveling along a wire and reflections causedwhen multiple elements are connected to the wire. Signal skew occurswhen signals travel along wires having different lengths and/orcharacteristics and arrive at an end point at different times. Crosstalk refers to the unwanted coupling of signals on wires that are inclose proximity. Cross talk becomes more of a problem as the operatingspeed of the memory device increases.

Therefore, there is a need in the art for memory modules, for use inmobile electronic devices, and solid-state drive applications that haveincreased memory capacities and/or operating speeds while minimizing thenumber input pins and wires required to access the memory modules.

SUMMARY OF THE INVENTION

The following represents a simplified summary of some embodiments of theinvention in order to provide a basic understanding of various aspectsof the invention. This summary is not an extensive overview of theinvention. It is not intended to identify key or critical elements ofthe invention or to delineate the scope of the invention. Its solepurpose is to present some embodiments of the invention in simplifiedform as a prelude to the more detailed description that is presentedbelow.

In accordance with aspects of the invention, semiconductor memorydevices with multiple memory banks and multiple serial data linkinterfaces are disclosed. In one example, a memory device is comprisedof a control module that independently controls data transfer betweenlink interfaces and memory banks. In some examples, the memory banks arenon-volatile memory. The control module of the invention communicateswith various other modules and circuitry in the memory device. Forexample, the control module generates control signals that drive many ofthe other modules.

Methods of implementing concurrent memory operations in semiconductorflash memory devices are also disclosed. A status indicator for eachserial data link interface and memory bank are also included. Thesestatus indicators are updated when the memory bank is busy (or returnsto ready) and when a link interface is busy (or returns to ready). Inaddition, a virtual multiple link feature permits a memory device withreduced pins to operate with greater throughput than prior art devices.

In accordance with aspects of the invention, a memory system having aplurality of cascaded memory devices is also disclosed. The memorydevices can be serially connected, and an external memory controller canreceive and provide data and control signals to the memory system. Inother embodiments of the invention, computer-executable instructions forimplementing the disclosed methods are stored as control logic orcomputer-readable instructions on computer-readable media, such as anoptical or magnetic disk. Various other aspects of the invention arealso disclosed throughout the specification.

In accordance with aspects of the invention, a memory device isdisclosed. The memory device includes flash memory, read circuitryconfigured to obtain read data from said flash memory to facilitatesubsequent transmission of the read data, and an output bufferconfigured to receive the read data and to transmit the read datathrough an output port in response to an output enable signal. Theoutput enable signal is held at a logic level for a period of time thatdelineates a length of said data transmitted from said output port. Thememory device can include a clock input configured to receive a clocksignal having edges, and additional circuitry configured to clock outthe read data from said output port in tandem with said edges for aduration of time corresponding to the period of time the output enablesignal is held at the logic level. The read data transmitted from saidoutput port can include a first data stream and a second data stream,the first data stream being delineated from the second data stream basedon a logic level of the output enable signal.

In accordance with other aspects of the invention, a method forproviding a data stream is disclosed. The method includes driving anoutput enable signal to an active state for a period of time, where theperiod of time substantially corresponds to a number of bits of data tosequentially appear at an output port of a flash memory device, thenumber of bits being up to a page buffer in size, and transmitting thenumber of bits of data from the output port for the period of time. Themethod can include receiving a free-running clock having inactive toactive and active to inactive transitions such that one bit of the datafrom the output port is transmitted on each of the inactive to activetransitions of the free-running clock during the period of time.Furthermore, a first bit of the data can be provided within a firstclock period while the output enable signal is driven to the activestate within the first clock period, and a last bit of the data isprovided within a second clock period while the output enable signal isdriven to an inactive state within the second clock period. Alternately,a first bit of the data can be provided at a first predetermined delayafter the output enable signal is driven to the active state, and a lastbit of the data can be provided at a second predetermined delay afterthe output enable signal is driven to an inactive state.

In accordance with another aspect of the invention, a memory system isdisclosed. The memory system includes a controller, a number of memorydevices, a clock input, read circuitry, an output buffer, and additionalcircuitry. Each of the memory devices includes flash memory. The readcircuitry is configured to obtain read data from the flash memory tofacilitate subsequent transmission of the read data. The output bufferis configured to receive the read data and to transmit the read datathrough an output port in response to an output enable signal. Theoutput enable signal is held at a logic level for a period of time thatdelineates a length of said read data transmitted from said output port.The additional circuitry is configured to clock out the read data fromsaid output buffer in tandem with said edges for a duration of timecorresponding to the period of time the output enable signal is held atthe logic level.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example and not limitedin the accompanying figures in which like reference numerals indicatesimilar elements and in which:

FIGS. 1A, 1B, 1C illustrate high level diagrams showing illustrativememory devices that allow for concurrent operations, in accordance withvarious aspects of the invention.

FIG. 2A is a high-level block diagram of an illustrative memory devicein accordance with aspects of the invention.

FIG. 2B is a schematic of a serial data link shown in FIG. 2 a,according to an embodiment of the present invention.

FIG. 2C is a schematic of an input serial to parallel register blockshown in FIG. 2A, according to an embodiment of the present invention.

FIG. 2D is a schematic of a path switch circuit shown in FIG. 2A,according to an embodiment of the present invention.

FIG. 2E is a schematic of an output parallel to serial register blockshown in FIG. 2A, according to an embodiment of the present invention.

FIGS. 3A, 4, 5A, 6A, and 7 illustrate timing diagrams for memoryoperations performed by a memory device in accordance with variousaspects of the invention. FIGS. 3B, 5B, and 6B are flowchartsillustrating the memory operations of FIGS. 3A, 5A, and 6A,respectively, in a memory device in accordance with various aspects ofthe invention.

FIGS. 8A, 8B, and 8C illustrate timing diagrams for concurrent memoryoperations performed in a memory device in accordance with variousaspects of the invention.

FIGS. 9 and 10 are flowcharts diagramming a method of controlling datatransfer between a plurality of serial data link interfaces and aplurality of memory banks in accordance with various aspects of theinvention.

FIG. 11 illustrates a block diagram of the pin-out configuration of amemory device in accordance with various aspects of the invention.

FIG. 12 illustrates a timing diagrams for a memory operations performedin a memory device equipped with various aspects of the virtual multiplelink feature in accordance with the invention.

FIG. 13 depicts a high-level block diagram of a cascaded configurationof numerous memory devices in accordance with various aspects of theinvention.

FIG. 14 illustrates a simplified timing diagram for a memory operationperformed on a memory device in a cascaded configuration in accordancewith aspects of the invention.

DETAILED DESCRIPTION

A serial data interface for a semiconductor memory having at least twomemory banks is disclosed. The serial data interface can include one ormore serial data links in communication with centralized control logic,where each serial data link can receive commands and data serially, andcan provide output data serially. Each serial data link can access anymemory bank in the memory for programming and reading of data. At leastone advantage of a serial interface is a low-pin-count device with astandard pin-out that is the same from one density to another, thus,allowing compatible future upgrades to higher densities without boardredesign.

FIGS. 1A and 1B are high level diagrams showing illustrative memorydevices that support concurrent operations, in accordance with variousaspects of the invention. FIG. 1A shows a memory device having multipleserial data link interfaces 102 and 104 and multiple memory banks 106and 108. The presently shown arrangement is referred to herein as a dualport configuration. Each serial data link interface has an associatedinput/output pin and data input and data output circuitry, which will bedescribed in further detail with respect to FIG. 2A. Data transferredthrough a serial data link interface passes through in a serial fashion(e.g., as a single-bit-wide stream of data.) Each of the data linkinterfaces 102 and 104 in the memory device are independent and cantransfer data to and from any of the memory banks 106 and 108. Forexample, serial data link 102 can transfer data to and from memory bank106 or memory bank 108. Similarly, serial data link 104 can transferdata to and from memory bank 106 and memory bank 108. Since the twoserial data link interfaces shown are independent, they can concurrentlytransfer data to and from separate memory banks. Link, as used herein,refers to the circuitry that provides a path for, and controls thetransfer of, data to and from one or more memory banks. A control module110 is configurable with commands to control the exchange of databetween each serial data link interface 102 and 104 and each memory bank106 and 108. For example, control module 110 can be configured to allowserial data link interface 102 to read data from memory bank 106 at thesame time that serial data link interface 104 is writing data to memorybank 108. This feature provides enhanced flexibility for system designand enhanced device utilization (e.g., bus utilization and coreutilization). As will be shown later, control module 110 can includecontrol circuits, registers and switch circuits.

FIG. 1B shows an embodiment in which a single serial data link interface120 is linked to multiple memory banks 122 and 124 via a control module126. This presently shown arrangement is referred to herein as a singleport configuration, and utilizes less memory device input/output pinsthan the dual port configuration shown in FIG. 1A. Control module 126 isconfigured to perform or execute two operating processes or threads, sothat serial data link interface 120 can exchange data with memory banks122 and 124 in a pipelined fashion. For example, while data is beingwritten into memory bank 122, data link interface 120 can be readingdata out of memory bank 124. In accordance with various aspects of theinvention and as will be described in further detail below, the memorydevice emulates multiple link operations using a single linkconfiguration with illustrated in FIG. 1B. Using this single link inconjunction with multiple banks configuration, also referred to hereinas a virtual multiple link, any available bank can be accessed while theother bank may be in a busy state. As a result, the memory device canachieve enhanced utilization of the single link configuration byaccessing the other available bank through link arbitration circuitry.

The memory devices shown in FIGS. 1A and 1B include two memory banks forillustration purposes only. One skilled in the art will appreciate thatseveral aspects of the invention disclosed herein are scalable and allowfor the use of multiple memory banks and multiple serial data linkinterfaces. A single memory device may include, for example, 2, 4, ormore memory banks. FIG. 1C shows an embodiment in which four independentserial data links 132, 134, 136 and 138 are configured to exchange datawith four memory banks 140, 142, 144 and 146 under the control of acontrol module 150. With a virtual multiple link configuration only onelink is necessary, so the remaining links (e.g., in FIG. 1A dual link orFIG. 1C quad link pinout configurations) are not used and may beconsidered as NC (i.e., No Connection). At least one advantage of aserial data link interface compared to a conventional parallel interfacestructure, is the reduced number of pins on the memory device while linkflexibility and large density are maintained. For example, while aconventional flash memory device may require 48 pins over multiple sidesof a package, a memory device in accordance with aspects of theinvention may utilize fewer pins (e.g., 11 pins) on a single side of astandard package 1100, as illustrated in FIG. 11. Alternately, adifferent and smaller type of package can be used instead, since thereare less internal bond pads that are required.

FIG. 2A illustrates a more detailed schematic diagram of the memorydevice shown in FIG. 1A, according to one embodiment of the presentinvention. The architecture of each memory bank in the memory device 200may be the same or similar to a NAND Flash memory core architecture.FIG. 2A illustrates those circuits which are relevant to the invention,and intentionally omits certain circuit blocks to simplify FIG. 2A. Forexample, memory device 200 implemented with a Flash memory corearchitecture will include high voltage generator circuits that arenecessary for programming and erasing the memory cells. Corearchitecture (or core circuitry), as used herein, refers to circuitryincluding memory cell array and associated access circuitry such asdecoding and data transfer circuitry. As standard memory architecturesare well known, so are the native operations associated with theselected architecture, which should be understood by any person skilledin the art. It should be further understood by those of skill in the artthat any known non-volatile or volatile memory architecture can be usedin alternative embodiments of the present invention.

Memory device 200 includes a multiplicity of identical memory banks withtheir respective data, control and addressing circuits, such as memorybank A 202 and memory bank B 204, an address and data path switchcircuit 206 connected to both memory banks 202 and 204, and identicalinterface circuits 205 and 207, associated with each memory bank forproviding data to and for receiving data from the switch circuit 206.Memory banks 202 and 204 are preferably non-volatile memory, such asFlash memory, for example. Logically, the signals received and providedby memory bank 202 are designated with the letter “A”, while the signalsreceived and provided by memory bank 204 are designated with the letter“B”. Similarly, the signals received and provided by interface circuit205 are designated with the number “0”, while the signals received andprovided by interface circuit 207 are designated with the number “1”.Each interface circuit 205/207 receives access data in a serial datastream, where the access data can include a command, address informationand input data for programming operations, for example. In a readoperation, the interface circuit will provide output data as a serialdata stream in response to a read command and address data. The memorydevice 200 further includes global circuits, such as a control interface208 and status/ID register circuit 210, which provide global signalssuch as clock signal sclki and reset to the circuits of both memorybanks 202 and 204 and the respective interface circuits 205 and 207. Afurther discussion of the aforementioned circuits now follows.

Memory bank 202 includes well known memory peripheral circuits such assense amplifier and page buffer circuit block 212 for providing outputdata DOUT_A and for receiving input program data DIN_A, and row decoderblock 214. Those of skill in the art will understand that block 212 willalso include column decoder circuits. A control and predecoder circuitblock 216 receives address signals and control signals via signal lineADDR_A, and provides predecoded address signals to the row decoders 214and the sense amplifier and page buffer circuit block 212.

The peripheral circuits for memory bank 204 are identical to thosepreviously described for memory bank 202. The circuits of memory bank Binclude a sense amplifier and page buffer circuit block 218 forproviding output data DOUT_B and for receiving input program data DIN_B,a row decoder block 220, and a control and predecoder circuit block 222.Control and predecoder circuit block 222 receives address signals andcontrol signals via signal line ADDR_B, and provides predecoded addresssignals to the row decoders 220 and the sense amplifier and page buffercircuit block 222. Each memory bank and its corresponding peripheralcircuits can be configured with well known architectures.

In general operation, each memory bank is responsive to a specificcommand and address, and if necessary, input data. For example, memorybank 202 will provide output data DOUT_A in response to a read commandand a read address, and can program input data in response to a programcommand and a program address. Each memory bank can be responsive toother commands such as an erase command, for example.

In the presently shown embodiment, path switch 206 is a dual portcircuit which can operate in one of two modes for passing signalsbetween the memory banks 202 and 204, and the interface circuits 205 and207. First is a direct transfer mode where the signals of memory bank202 and interface circuit 205 are passed to each other. Concurrently,the signals of memory bank 204 and interface circuit 207 are passed toeach other in the direct transfer mode. Second is a cross-transfer modewhere the signals of memory bank 202 and interface circuit 207 arepassed to each other. At the same time, the signals of memory bank 204and interface circuit 205 are passed to each other. A single portconfiguration of path switch 206 will be discussed later.

As previously mentioned, interface circuits 205 and 207 receive andprovide data as serial data streams. This is for reducing the pin-outrequirements of the chip as well as to increase the overall signalthroughput at high operating frequencies. Since the circuits of memorybanks 202 and 204 are typically configured for parallel address anddata, converting circuits are required.

Interface circuit 205 includes a serial data link 230, input serial toparallel register block 232, and output parallel to serial registerblock 234. Serial data link 230 receives serial input data SIP0, aninput enable signal IPE0 and an output enable signal OPE0, and providesserial output data SOP0, input enable echo signal IPEQ0 and outputenable echo signal OPEQ0. Signal SIP0 (and SIP1) is a serial data streamwhich can each include address, command and input data. Serial data link230 provides buffered serial input data SER_IN0 corresponding to SIPOand receives serial output data SER_OUT0 from output parallel to serialregister block 234. The input serial-to-parallel register block 232receives SER_IN0 and converts it into a parallel set of signals PAR_IN0.The output parallel-to-serial register block 234 receives a parallel setof output data PAR_OUT0 and converts it into the serial output dataSER_OUT0, which is subsequently provided as data stream SOP0. Outputparallel-to-serial register block 234 can also receive data fromstatus/ID register circuit 210 for outputting the data stored thereininstead of the PAR_OUT0 data. Further details of this particular featurewill be discussed later. Furthermore, serial data link 230 is configuredto accommodate daisy chain cascading of the control signals and datasignals with another memory device 200.

Serial interface circuit 207 is identically configured to interfacecircuit 205, and includes a serial data link 236, inputserial-to-parallel register block 240, and output parallel-to-serialregister block 238. Serial data link 236 receives serial input dataSIP1, an input enable signal IPE1 and an output enable signal OPE1, andprovides serial output data SOP1, input enable echo signal IPEQ1 andoutput enable echo signal OPEQ1. Serial data link 236 provides bufferedserial input data SER_IN1 corresponding to SIP1 and receives serialoutput data SER_OUT1 from output parallel-to-serial register block 238.The input serial-to-parallel register block 238 receives SER_IN1 andconverts it into a parallel set of signals PAR_IN1. The outputparallel-to-serial register block 240 receives a parallel set of outputdata PAR_OUT1 and converts it into the serial output data SER_OUT1,which is subsequently provided as data stream SOP1. Output parallel toserial register block 240 can also receive data from status/ID registercircuit 210 for outputting the data stored therein instead of thePAR_OUT1 data. As with serial data link 230, serial data link 236 isconfigured to accommodate daisy chain cascading of the control signalsand data signals with another memory device 200.

Control interface 208 includes standard input buffer circuits, andgenerates internal chip select signal chip_sel, internal clock signalsclki, and internal reset signal reset, corresponding to CS#, SCLK andRST# respectively. While signal chip_sel is used primarily by serialdata links 230 and 236, reset and sclki are used by many of the circuitsthroughout memory device 200.

FIG. 2B is a schematic of serial data link 230, according to anembodiment of the invention. Serial data link 230 includes input buffers242 for receiving input signals OPE0, IPE0 and SIP0, output drivers 244for driving signals SOP0, IPEQ0 and OPEQ0, flip-flop circuits 246 forclocking out signals out_en0 and in_en0, inverter 248 and multiplexor(MUX) 250. The input buffers for signals OPE0 and SIP0 are enabled inresponse to chip_sel, and the output driver for signal SOP0 is enabledin response to an inverted chip_sel via inverter 248. Signal out_en0enables an output buffer, which is shown later in FIG. 2E and providessignal SER_OUT0. Signal in_en0 enables the input serial to parallelregister block 232 to latch SER_IN0 data. Signals in_en0, out_en0 andSER_IN0.

Serial data link 230 includes circuits to enable daisy chain cascadingof the memory device 200 with another memory device. More specifically,the serial input data stream SIP0, and enable signals OPE0 and IPE0 canbe passed through to the corresponding pins of another memory devicethrough serial data link 230. SER_NO is received by AND logic gate 252and passed to its corresponding flip-flop 246 when in_en0 is at theactive high logic level. Simultaneously, in_en0 at the active high logiclevel will control MUX 250 to pass Si_next0 to output driver 244.Similarly, IPE0 and OPE0 can be clocked out to IPEQ0 and OPEQ0 throughrespective flip-flops 246. While serial data link 230 has beendescribed, it is noted that serial data link 240 includes the samecomponents, which are interconnected in the same way as shown for serialdata link 230 in FIG. 2B.

FIG. 2C is a schematic of the input serial to parallel register block232. This block receives the clock signal sclki, the enable signalin_en0 and the input data stream SER_IN0, and converts SER_IN0 intoparallel groups of data. In particular, SER_IN0 can be converted toprovide a command CMD_0, a column address C_ADD0, a row address R_ADD0and input data DATA_IN0. The presently disclosed embodiment of theinvention preferably operates at a high frequency, such as at 200 MHzfor example. At this speed, the serial input data stream can be receivedat a rate faster than the received command can be decoded. It is forthis reason that the serial input data stream is initially buffered in aset of registers. It should be understood that the presently shownschematic also applies to input serial to parallel register block 240,where the only difference lies in the designator of the signal names.

The input serial-to-parallel register block 232 includes an inputcontroller 254 for receiving in_en0 and sclki, a command register 256, atemporary register 258, and a serial data register 260. Since the datastructure of the serial input data stream is predetermined, specificnumbers of bits of the input data stream can be distributed to theaforementioned registers. For example, the bits corresponding to acommand can be stored in the command register 256, the bitscorresponding to row and column addresses can be stored in the temporaryregister 258, and the bits corresponding to input data can be stored inthe serial data register 260. The distribution of the bits of the serialinput data stream can be controlled by input controller 254, which caninclude counters for generating the appropriate register enablingcontrol signals after each predetermined number of bits have beenreceived. In other words, each of the three registers can besequentially enabled to receive and store bits of data of the serialinput data stream in accordance with the predetermined data structure ofthe serial input data stream.

A command interpreter 262 receives a command signal in parallel fromcommand register 256, and generates a decoded command CMD_0. Commandinterpreter 262 is a standard circuit implemented with interconnectedlogic gates or firmware, for decoding the received commands. As shown inFIG. 4, CMD_0 can include signals cmd_status and cmd_id. A switchcontroller 264 receives one or more signals from CMD_0 to control asimple switch circuit 266. Switch circuit 266 receives all the datastored in the temporary register 258 in parallel, and loads one or bothof column address register 268 and row/bank register 270 with data inaccordance with the decoded command CMD_0. This decoding is preferablydone because the temporary register may not always include both columnand row/bank address data. For example, a serial input data streamhaving a block erase command will only use a row address, in which caseonly the relevant bits stored in the temporary register 258 are loadedinto row/bank register 270. The column address register 268 providesparallel signal C_ADD0, the row/bank address register 270 providesparallel signal R_ADD0, and data register 272 provides parallel signalDATA_IN0, for programming operations. Collectively, CMD_0, C_ADD0,R_ADD0 and DATA_IN0 (optional), form the parallel signal PAR_IN0. Bitwidths for each of the parallel signals have not been specified, as thedesired width is a design parameter which can be customized, or tailoredto adhere to a particular standard.

Examples of some of the operations of the memory device 200 for a Flashcore architecture implementation are shown in Table 1 below. Table 1lists possible OP (operation) codes for CMD_0 and corresponding statesof the column address (C_ADD0), row/bank address (R_ADD0), and the inputdata (DATA_IN0).

TABLE 1 Command Set OP Column Row/Bank Input Data Code Address Address(1 Byte to Operation (1 Byte) (2 Bytes) (3 Bytes) 2112 Bytes) Page Read00h Valid Valid — Random Data Read 05h Valid — — Page Read for Copy 35h— Valid — Target Address 8Fh — Valid — Input for Copy Serial Data Input80h Valid Valid Valid Random Data Input 85h Valid — Valid Page Program10h — — — Block Erase 60h — Valid — Read Status 70h — — — Read ID 90h —— — Write Configuration A0h — — Valid (1 Byte) Register Write DN (DeviceB0h — — — Name) Entry Reset FFh — — — Bank Select 20h — Valid (Bank) —

Furthermore, Table 2 shows the preferred input sequence of the inputdata stream. The commands, addresses, and data are serially shifted inand out of the memory device 200, starting with the most significantbit. Command sequences start with a one-byte command code (“cmd” inTable 2). Depending on the command, the one-byte command code may befollowed by column address bytes (“ca” in Table 2), row address bytes(“ra” in Table 2), bank address bytes (“ba” in Table 2), data bytes(“data” in Table 2), and/or a combination or none.

TABLE 2 Input Sequence in Byte Mode 1^(st) 2^(nd) 3^(rd) 4^(th) 5^(th)6^(th) 7^(th) 2115^(th) 2118^(th) Operation Byte Byte Byte Byte ByteByte Byte . . . Byte . . . Byte Page Read cmd ca Ca ba/ra ra ra — — — —— Random Data cmd ca Ca — — — — — — — — Read Page Read for cmd ba/ra Rara — — — — — — — Copy Target Address cmd ba/ra Ra ra — — — — — — — Inputfor Copy Serial Data cmd ca Ca ba/ra ra ra data . . . data . . . dataInput Random Data cmd ca Ca data data data data . . . data — — InputPage Program cmd — — — — — — — — — — Block Erase cmd ba/ra Ra ra — — — —— — — Read Status cmd — — — — — — — — — — Read ID cmd — — — — — — — — —— Write cmd data — — — — — — — — — Configuration Register Write DN Entrycmd — — — — — — — — — — Reset cmd — — — — — — — — — — Bank Select cmd ba— — — — — — — — —

FIG. 2D is a schematic of path switch 206 shown in FIG. 2A. Switch 206is logically divided into two switch sub-circuits 274 and 276, which areidentically configured. Switch sub-circuit 274 includes four inputmultiplexors 278 that selectively pass the commands, addresses and inputdata of either interface circuit 205 or interface circuit 207 to thecircuits of memory bank 202. These signals have been previously groupedin FIG. 2C as PAR_IN0 by example. Switch sub-circuit 274 includes oneoutput multiplexor 280 for selectively passing the output data fromeither memory bank 202 or memory bank 204 to interface circuit 205.Switch sub-circuit 276 includes four input multiplexors (not shown) thatselectively pass the commands, addresses and input data of eitherinterface circuit 205 or interface circuit 207 to the circuits of memorybank 204. Switch sub-circuit 276 includes one output multiplexor (notshown) for selectively passing the output data from either memory bank202 or memory bank 204 to interface circuit 207.

Both switch sub-circuits 274 and 276 can simultaneously operate in thedirect transfer mode or the cross-transfer mode, depending on the stateof switch control signal SW_CONT. Path switch circuit 206 is presentlyshown in a dual port configuration, meaning that both memory banks 202and 204 can be simultaneously accessed through either interface circuits205 and 207.

According to another embodiment of the present invention, as previouslyillustrated in FIG. 1B, path switch 206 can operate in a single portmode in which only one of interface circuits 205 and 207 is active. Thisconfiguration can further reduce the pin-out area requirements of thememory device 200 since the input/output pads associated with the unusedinterface circuit are no longer required. In the single portconfiguration, switch sub-circuits 274 and 276 are set to operate in thedirect transfer mode only, with the exception of the respective outputmultiplexors 280 which can remain responsive to the SW_CONT selectionsignal.

In a single port embodiment where only interface circuit 205 is active,a supplemental path switch (not shown) is included in the input parallelto serial register block 232 (or block 234), for selectively passing thedata from the outputs of switch 266 and serial data register 260 to thecorresponding column, row/bank and data registers of either input serialto parallel register block 232 or 240. Effectively, the supplementalpath switch can be similar to switch 206. Hence, the column, row/bankand data registers of both input serial to parallel register blocks 232and 240 can be loaded with data for alternate memory bank accesses, orfor substantially concurrent accesses.

FIG. 2E is a schematic of output parallel-to-serial register block 234.It is noted that output parallel-to-serial register block 238 isidentically configured. Output parallel-to-serial register block 234provides either data accessed from the memory bank, or status datapreviously stored in registers. More specifically, the user or systemcan request a status of either serial data links 230 or 236. A value of‘1’ in a designated bit location (e.g., bit 4) in the outputted statusdata can indicate that the particular serial data link interface isbusy. The fixed data can further include chip identification data, whichwith the status data, can both be pre-loaded with default states uponpower up of the memory device 200. The status data can be configured tohave any preselected bit pattern that is recognizable by the system.Although not shown, FIG. 2E can include additional control circuitry forupdating one or more bits stored in register 284, based on one or morepredetermined conditions. For example, one or more status bits can bechanged based on a count of elapsed clock cycles, or based on acombination of one or more flag signals received from various circuitblocks of memory device 200.

Output parallel to serial register block 234 includes a firstparallel-to-serial register 282 for receiving output data PAR_OUTO frompath switch 206, a second parallel-to-serial register 284 for receivingfixed data from a multiplexor 286. Multiplexor 286 selectively passesone of the status data stored in status register 288 or chipidentification data stored in ID register 290 in response to signalcmd_id. An output multiplexor 292 passes the data from either the firstparallel-to-serial register 282 or the second parallel-to-serialregister 284 in response to either cmd_id or cmd_status being active,via OR gate 294. Finally, a serial output control circuit 296 enabled byout_en0 provides SER_OUT0.

One skilled in the art will appreciate that the size and location of thestatus indicator may be altered in accordance with various aspects ofthe invention. For example, the serial data link interface statusindicator may be joined with other types of status indicator (e.g.,memory bank status indicator) and/or physically located outside theregister block (e.g., in the link arbitration module or in the controlmodule 238). In another example, the serial data link interface statusindicator is a one-bit register.

FIGS. 3A, 4, 5A, 6A, and 7 illustrate example timing diagrams for somememory operations performed by memory device 200 in accordance withvarious aspects of the invention. Some memory commands performed by thememory device 200 include, but are not limited to, page read, randomdata read, page read for copy, target address input for copy, serialdata input, random data input, page program, block erase, read status,read ID, write configuration register, write device name entry, reset,and/or bank select. The following discussion of the timing diagrams ismade with reference to the previously described embodiments of thememory device 200 shown in the previous figures, and Tables 1 and 2.

In the example depicted in the timing diagram of FIG. 3A, a “page read”memory command 314 is received at serial data link 230 of a memorydevice 200 in accordance with the invention. Moreover, FIG. 3B shows asimplified flowchart paralleling the operation of the “page read” memorycommand 314 in the timing diagram of FIG. 3A. As a practical matter, thesteps illustrated in FIG. 3B will be discussed in conjunction with thetiming diagram of FIG. 3A. By way of example, in step 324, a “page read”memory command 314 is read in at serial data link 230 of the memorydevice 200.

The incoming data stream in this example is a six-byte serial datastream (i.e., serial input data) including command data (in the firstbyte), column address data (in the second and third bytes), and row andbank address data (in the fourth, fifth, and sixth bytes). The bankaddress can be used to determine access to either bank 202 or 204 viapatch switch 206. One skilled in the art will understand that differentmemory commands may have a different data stream. For example, a “randomdata read” memory command has a predetermined data stream of only threebytes: command data (in the first byte) and column address data (in thesecond and third bytes). In the latter example, the address field of theserial input data only contained column address data and was two byteslong. Meanwhile, in the former example, the address field was five byteslong. One skilled in the art will appreciate after review of theentirety disclosed herein that numerous memory commands andpredetermined data streams are apparent in accordance with variousaspects of the invention.

Continuing with the example involving the “page read” memory command asillustrated in FIG. 3 a, in response to the chip select (CS#) signal 302going low and the input port enable (IPEx) signal 306 going high, theserial input (SIPx) port 308 is sampled on the first falling edge of theserial clock (SCLK) signal 304 (where ‘x’ acts as a placeholderrepresenting the link interface number, e.g., link 0 interface 232 orlink 1 interface 234). The data read out (in step 328) is a data streamcorresponding to a “page read” memory command 314. The CS# signal 302 isan input into the memory device 200 and may be used, among other things,to indicate whether the memory device 200 is active (e.g., when CS# islow) or whether the memory device's serial outputs are at high impedance(e.g., when CS# is high). The IPEx signal 306 indicates whether anincoming data stream will be received at a particular link interface(e.g., when IPEx is high) or whether a particular link interface willignore the incoming data stream (e.g., when IPEx is low). The incomingdata stream is received at the memory device at the SIPx 308 of a linkinterface. Finally, the system clock (SCLK) signal 304 is an input intothe memory device 200 and is used to synchronize the various operationsperformed by the numerous circuits of the memory device 200. It will beapparent to one skilled in the art that a memory device in accordancewith various aspects of the invention may be synchronized with such aclock signal (e.g., operations and data transfers occur at the risingand/or falling edge of the clock signal) or may be asynchronous (i.e.,not synchronous). In the example of FIG. 3A, however, input data islatched on the falling edge of SCLK and output data 322 appears on theserial output pin 312 SPOx after the rising edge of SCLK. The status ofthe “page read” can be checked on the SPOx pin 312 as shown in FIG. 3A,whereby a “bank busy” result will be provided on SPOx until a time 318when a “ready” indication will appear, and the output data will shortlyappear during a time 322. It should be noted that although FIG. 3Aillustrates a “page read” with subsequent “read status”, a “page read”without a “read status” is also contemplated in accordance with aspectsof the invention. In that embodiment, no data would be provided on theSPOx pin until output data would be ready.

The command data sampled by SIPx 308 is written to the appropriateregister (e.g., command register 256) in FIG. 2C. At least one benefitto the option of designing the incoming data stream such that the firstbyte is command data is that the data can be transferred to the commandregister without additional processing. Subsequent bytes in the datastream may be address data and/or input data according to the type ofmemory command. One skilled in the art will appreciate that the set ofmemory commands recognized by a memory device in accordance with variousaspects of the invention may be defined by word-basis (i.e., 16 bits) orany I/O width. In FIG. 3A, the command data (i.e., 00h corresponding to“page read” 314) is followed by five bytes of address data: two bytes ofcolumn address data and three bytes of row/bank address data. Theaddress data is written to an address register 258 in FIG. 2C. Theaddress data is used to locate the data stored in the memory bank 202that is to be read. The pre-decoder circuit 216, column decoder incircuit 212, and row decoder 214, are utilized during this process toselect the data to be read. For example, the pre-decoder module 214 isused to pre-decode the address information. Subsequently, the columndecoder in circuit 212 and row decoder 214 are used to activate thebitline and wordline corresponding to the address data. In the case of a“page read” command, multiple bitlines are activated corresponding to awordline. Subsequently, the data stored in the memory bank 202 istransferred to a page register in circuit 212 after being sensed bysense amplifiers. The data in the page register may not be availableuntil time 318 in FIG. 3A, i.e. the output pin SPOx will indicate“busy”. The amount of time lapsed is referred to as the transfer time(t_(R)). The transfer time period ends at time 318 (in FIG. 3A) andlasts for a duration of t_(R).

Before the transfer time period elapses, a memory bank status indicatoris set to indicate that the particular memory bank (e.g., memory bank202) is “busy”. The illustrative memory bank status indicator of FIG. 3Ais a 1-byte field with one of the bits (e.g., bit 4) indicating whethermemory bank 202 (i.e., bank 0) is “busy” or “ready”. The memory bankstatus indicator is stored in a status register 288 of FIG. 2E. Thememory bank status indicator is updated (e.g., bit 4 is set to ‘0’)after a memory bank has been identified from the incoming data stream.Once the memory operation is complete, the bank status indicator isupdated (e.g., bit 4 is set to ‘1’) to indicate that the memory bank isno longer “busy” (i.e., “ready”). Note that both the bank statusindicator as well as the SPOx output pin will indicate the “busy” statusas will be explained in further detail below. One of skill in the artwill appreciate that although the memory bank status indicator isdepicted in FIG. 3A as a 1-byte field, its size is not necessarily solimited. At least one benefit of a larger status indicator is theability to monitor the status of a greater quantity of memory banks. Inaddition, the status indicator may be used to monitor other types ofstatus (e.g., whether the memory bank is in a “pass” or “fail” statusafter a memory operation, such as a “page program”, was performed). Inaddition, it will be apparent to one skilled in the art that the statusindicator of this example being implemented such that each bitdesignates the status of a different memory bank is exemplary only. Forexample, the value of a combination of bits may be used to indicate thestatus of a memory bank (e.g., by using logic gates and othercircuitry). The operation of the “read status” command corresponding tothe memory bank status indicator is discussed in relation to FIG. 7below.

The memory bank status indicator in the example of FIG. 3A is read usingthe “read status” memory command 316 (in step 328). Sometime during thetransfer time period, a “read status” command 316 is sent to the commandregister in the register block 224. The “read status” command instructsthe memory device 200 to monitor the status of the memory bank 202 todetermine when the transfer of data from the memory bank 202 to a pageregister 216 is complete. The “read status” command is sent from thecontrol module 238 through the data path control module 230 or directlyby the data path control module 230. Once the “read status” command hasbeen issued (e.g., sent to a command interpreter 228 and/or controlmodule 238) the output port enable (OPEx) signal 310 is driven high andthe contents of the memory bank status indicator are outputted throughthe serial output (SOPx) port 312. Similar to the IPEx signal 306, theOPEx signal 310 enables the serial output port buffer (e.g., the dataoutput register) when set to high. At time 318 in FIG. 3A, the statusindicator data in the SOPx indicates that the memory bank 202 haschanged (in step 330) from a “busy” status to a “ready” status. The OPExsignal 310 is returned to low since the content of the status indicatoris no longer needed.

Next in FIG. 3A, the IPEx signal is set high, and a “page read” command320 with no trailing address data is re-issued (in step 332) to thecommand register in the register block 224 in order to provide data fromthe data registers to the output pin SPOx. Subsequently, the OPEx signalis set high (and IPEx is returned to low), and the contents of the pageregister 216 are transferred to the SOPx 312. The output data isprovided (in step 334) through the link interface 230 out of memorydevice 200. Error correction circuitry (not shown in the Figures) cancheck the output data and indicate a read error if an error is detected.Those skilled in the art will understand that the monitoring of thestatus and re-assertion of the page read command can be automaticallydone by the system. FIG. 3A is merely one example of memory deviceoperation in accordance with aspects of the invention, and the inventionis not so limited. For example, other memory commands and timingdiagrams are envisioned in accordance with various aspects of theinvention.

For example, in FIG. 4, a simplified timing diagram for the “random dataread” command following a “page read” command is illustrated. The“random data read” command enables the reading of additional data at asingle or multiple column addresses subsequent to a “page read” commandor a “random data read” command. The data stream for a “random dataread” command 402 is comprised of three bytes: command data (in thefirst byte) and column address data (in the second and third bytes). Norow address data is required since data will be read from the same rowselected in the “page read” command. A “random data read” command issuedafter a normal “page read” command has completed results in some of thedata 404 from the current page (i.e., the page read during the earliercommand) being outputted. At least one benefit to the “random data read”command is the increased efficiency with which data from the preselectedpage may be outputted since the data is already present in a pageregister of circuit 212 corresponding to the memory bank 202.

Regarding FIG. 5A, a timing diagram for the “page program” command isillustrated. Since the embodiment illustrated in FIG. 2A utilizes aserial data input and output link structure, prior to beginning toprogram a page, the program data must first be loaded into a bank pageregister. This is accomplished with the “serial data input command”. The“serial data input” command 502 is comprised of a serial data loadingperiod during which up to a page (e.g., 2,112 bytes) of data is loadedinto the page buffer in circuit 212. After the process of loading thedata register is complete, a “page start” command 504 is issued totransfer the data from the bank register into the appropriate memorybank. Once command 504 is issued, the internal write state machineexecutes an appropriate algorithm and controls timing to program andverify the operation. Therefore, according to an embodiment of theinvention, a “page start” command is divided into two steps: serial datainput and verification. Upon successful completion of a “page program”command, the memory bank status indicator will provide a “pass” (asopposed to a “fail”) result to indicate a successful operation. In otherrespects, the timing diagram and steps involving in the example of FIG.5A are similar to those of FIG. 3A, which was previously described ingreater detail.

Moreover, FIG. 5B shows a simplified flowchart paralleling the operationof the “page program” command in the timing diagram of FIG. 5A. In step506, the “serial data input” command 502 is input to the serial inputport (SIP) line. The data stream input to the SIP line in this exampleis a multi-byte serial data stream (i.e., serial input data) beginningwith the command data (in the first byte). Next, the column address data(in the second and third bytes of the serial data stream) and rowaddress/bank data (in the fourth, fifth, and sixth bytes of the serialdata stream) are input (in step 508) to the SIP line. Then, the inputdata is input (in step 510) to the SIP line in the subsequent bytes ofthe serial data stream. In step 512, a “program start” command 504 isissued. Next, to monitor the status of the operation, a “read status”command is written to the SIP line (in step 514). This results in thememory device monitoring the status bits of the memory bank statusregister. Once the status bits indicate that the memory bank is ready(in step 516) and that the memory bank indicates a “pass” (in step 518),then the “page program” memory command has been successfully performed.

In addition, the “page read for copy” and “target address input forcopy” memory commands are others operations performed by a memory devicein accordance with aspects of the invention. If the “page read for copy”command is written to the command register of a serial link interface,then the internal source address (in 3 bytes) of the memory location iswritten. Once the source address is inputted, the memory devicetransfers the contents of the memory bank at the specified sourceaddress into a data register. Subsequently, the “target address inputfor copy” memory command (with a 3-byte bank/row address sequence) isused to specify a target memory address for the page copy operation. A“page program” command may then be used to cause the internal controllogic to automatically write the page data to the target address. A“read status” command can be subsequently used to confirm the successfulexecution of the command. Other memory operations will be apparent toone skilled in the art after review of the entire disclosure herein.

Regarding FIG. 6A, a timing diagram for the “erase” (or “block erase”)command is illustrated. In addition, FIG. 6B shows a simplifiedflowchart paralleling the operation of the “erase” command in the timingdiagram of FIG. 6A. One skilled in the art is aware that erasingtypically occurs at the block level. For example, a Flash memory device200 can have, at each bank, 2,048 erasable blocks organized as 642,112-byte (2,048+64 bytes) pages per block. Each block is 132K bytes(128K+4K bytes). The “erase” command operates on one block at a time.Block erasing is started by writing command data 602 at step 610corresponding to the “erase” command (i.e., command data of ‘60h’) tothe command register via SIPx along with three bytes for row and bankaddresses at step 612. After the command and address input arecompleted, the internal erase state machine automatically executes theproper algorithm and controls all the necessary timing to erase andverify the operation. Note that the “erase” operation may be executed bywriting or programming a logic value of ‘1’ to every memory location ina block of memory. In order to monitor the erase status to determinewhen the t_(BERS) (i.e., block erase time) is completed, the “readstatus” command 604 (e.g., command data corresponding 70h) may be issuedat step 614. After a “read status” command, all read cycles will be fromthe memory bank status register until a new command is given. In thisexample, the appropriate bit (e.g., bit 4) of the memory bank statusregister reflects the state (e.g., busy or ready) of the correspondingmemory bank. When the bank becomes ready at step 618, the appropriatebit (e.g., bit 0) of the memory bank status register is checked at step620 to determine if the erase operation passed (i.e., successfullyperformed) at step 622 or failed at step 624. In some respects, thetiming diagram and steps involving in the example of FIG. 6A are similarto those of FIG. 3A, which was previously described in greater detail.

Regarding FIG. 7, the memory bank status indicator is read using the“read status” memory command. When a “read status” command (i.e., ‘70h’)is sent at 702 to the command register 256 in FIG. 2C, the memory device200 is instructed to monitor the status of the memory bank 202 to, amongother things, determine when the transfer of data from the memory bank202 to the page buffer in circuit 212 is successfully completed. Oncethe “read status” command has been issued (e.g., sent to a commandinterpreter 262) the output port enable (OPEx) signal is driven high andthe contents of the memory bank status indicator are outputted at 704through the serial output (SOPx) port. The OPEx signal enables theserial output port buffer (e.g., the data output register) when set tohigh. In the example of FIG. 7, the memory bank status indicator is a1-byte (i.e., 8-bit) field with each bit indicating, among other things,whether a memory bank (e.g., memory bank 202) is “busy” or “ready”and/or whether a operation performed on a memory bank (e.g., “erase”command) is has “passed” or “failed”. One of skill in the art willappreciate that although the memory bank status indicator is depicted inFIG. 7 as a 1-byte field, its size is not necessarily so limited. Atleast one benefit of a larger status indicator is the ability to monitorthe status of a greater quantity of memory banks. In addition, it willbe apparent to one skilled in the art that although the status indicatorof this example was implemented such that each bit designated the statusof a different memory bank, the invention is not so limited. Forexample, the value of a combination of bits may be used to indicate thestatus of a memory bank (e.g., by using logic gates and othercircuitry).

FIGS. 8A, 8B, and 8C, illustrate timing diagrams for a memory device inaccordance with aspects of the invention being used to performconcurrent operations using dual independent serial data links 230 and236. Some concurrent operations performed by a memory device inaccordance with aspects of the invention include, but are not limitedto, concurrent read, concurrent program, concurrent erase, read whileprogram, read while erase, and program while erase. FIG. 8A illustratesa concurrent “page read” operation being performed on bank A (bank 202)and bank B (bank 204). In FIG. 8A, bank A is represented as “bank 0”while bank B is represented as “bank 1”. FIG. 8B. Other concurrentoperations will become apparent to one skilled in the art upon review ofthe entire disclosure herein.

Referring to FIG. 8A, concurrent “page read” operations 802, 804directed at different memory banks in a memory device 200 are executed.In a memory device 200 with dual data link interfaces 230, 236 a “pageread” command 804 is issued through data link interface 236 (i.e., link1) while a “page read” 802 is pending through data link interface 230(i.e., link 0). Although FIG. 8A shows the “page read” on bank 0starting before the “page read” on bank 1, the two “page read”operations can begin substantially simultaneously and operateconcurrently. The outputted data 806, 808 from each of the “page read”commands is simultaneously sent through their respective data linkinterfaces. Therefore, each data link interface in memory device 200 mayaccess any of the memory banks and operate independently. At least onebenefit of this feature is greater flexibility in system design and anenhancement on device utilization (e.g., bus utilization and coreutilization).

The path of the outputted data from the memory bank to the data linkinterface in FIG. 8A is similar to that of FIG. 3A discussed earlier.For example, the outputted data from memory bank 204 flows from S/A andpage buffer 218 through path switch 206 controlled by a bank address forexample, to output parallel-to-serial register block 240, and to serialdata link interface 236 (i.e., link 1). The simultaneous data transferbetween memory banks 202 and 204 and serial data link interfaces 230,236, respectively, will occur independently of each other. As the bankaddress can control path switch 206, serial data link interface 236 canaccess bank 202 instead. The number of data link interfaces in memorydevice 200 is not limited to the number of ports or pins on memorydevice 200. Nor is the number of link interfaces in memory device 200limited by the number of memory banks in the memory device. For example,each data link interface may process a single input stream and/or asingle output stream.

Furthermore, in accordance with various aspects of the invention, FIG.8B illustrates a timing diagram of a “page read” command 810 and a “pageprogram” command 812 directed at different memory banks in a memorydevice 200 being performed concurrently. In this example, a readoperation (“page read” 810) is being performed in one of the pluralityof memory banks (e.g., memory bank 202) through serial data linkinterface 230. Meanwhile, simultaneously, a write operation (“pageprogram” 812) is being performed in another of the plurality of memorybanks (e.g., memory bank 204) through serial data link interface 236. Inaccordance with various aspects of the invention, each link in thememory device 200 may access any of the memory banks and operateindependently.

FIG. 8C is an illustrative timing diagram of a memory device 200 withtwo serial data link interfaces and two memory banks performingconcurrent memory operations. First, an “erase” command 814 directed atmemory bank 0 (bank 202) is issued from serial interface link 0 (serialdata link 230). While link 0 (serial data link 230) and memory bank 0(bank 202) are busy with the “erase” command 814, a “page program”command is received at the memory device and directed to use link 1(serial data link 236). Thus, a “page program” command 816 is performedon memory bank 0 (bank 202) from serial data link interface 1 (serialdata link 236). Meanwhile, simultaneously, a read command 818 isperformed on memory bank 1 (bank 204) by serial data interface 0 (serialdata link 230). Data is transferred between serial data link interface 0(serial data link 230) and bank 0 (bank 202) during memory command 814and between the same link interface 0 (serial data link 230) and bank 1(bank 204) during memory command 818. Therefore, in accordance withaspects of the invention, each link in the memory device 200independently accesses any of the memory banks (i.e., memory banks thatare not busy).

It will be apparent to one skilled in the art, after review of theentirety disclosed herein, that FIGS. 8A, 8B, and 8C illustrate merelysome examples of concurrent memory operations envisioned in accordancewith the invention. Other examples of concurrent operations include, butare not limited to, concurrent erase, read while program, read whileerase, program while erase, erase while program, and/or concurrentprogram. One skilled in the art will recognize that the depiction of theorder of the steps in the flowchart should not be construed to limit thesteps to only that particular order. For example, read and programcommands can be issued with or without read status commands.

FIG. 9 shows a more general description of two concurrent writeoperations between a plurality of serial link interfaces and a pluralityof memory banks in accordance with aspects of the invention. FIG. 9illustrates a method of writing data via a serial data link interface toa memory bank in accordance with an embodiment of the invention. First,in step 902 a data stream is received at a serial data link interface.The data stream contains command, address and data that will be storedin registers. Next, in step 904 a serial data link interface statusindicator corresponding to the first serial data link interface isupdated to indicate that the first serial data link interface is beingutilized. Step 904 includes changing a bit value in the status register.The update in step 904 indicates that the particular interface is beingutilized. In step 906, the data stream is parsed to extract a firstmemory bank identifier. The memory bank identifier uniquely identifies amemory bank in the memory device. The memory bank identifier may beincluded within an address field or other field of the data stream.Next, after parsing the data stream to extract a memory bank identifier,in step 908 a corresponding memory bank status indicator is updated. Theupdating occurring in steps 904 and 908 can be driven by control signalsgenerated by control circuits within status/ID register 210 for example.These control signals have been omitted from the included timingdiagrams for simplicity. Finally, in step 910 the data is routed betweenthe first serial data link and the first memory bank. It should be notedthat step 910 has been simplified in this general description, sincedata is first written to a memory bank page register and thensubsequently programmed into the memory bank.

Meanwhile, another write data operation is performed on a differentmemory bank via a different serial data link interface concurrently withthe operation 902 shown. In other words, a second memory operation isconcurrently performed using a second data stream that is routed betweena second serial data link interface and a second memory bank. First asecond data stream is received at a second one of the plurality ofserial data link interfaces in step 912. The serial data link interfacesreferred to in steps 912 and 902 are all part of the same memory device.In step 914 a serial data link interface status indicator correspondingto the second data link interface is updated to indicate that the secondserial data link interface is being utilized. Next, the second datastream is parsed to extract a second memory bank identifier in step 916.A memory bank status indicator corresponding to the second memory bankidentifier is updated to indicate that the second memory bank is beingutilized in step 918 and in step 920 data is routed between the secondserial data link interface and the second memory bank via the secondmemory bank's associated page register, as previously described inrelation to the “page program” command. In FIG. 9, once the transfer ofdata has taken place, i.e., the serial data link interface has receivedall the data to be written into the designated memory bank, the serialdata link interface indicator corresponding to each serial data linkinterface will be reset to indicate that the associated link is nowavailable, while the memory bank indicator will remain busy until allassociated data has been programmed, after which the memory bankindicator will indicate that the associated bank has become available.

FIG. 10 comprises illustrative steps that may be performed when data isread from a memory bank concurrently with the writing of data shown insteps 902 to 910 in FIG. 9 (designated as steps 1010). FIG. 10illustrates an example of some of the steps that may be performed incompleting the concurrent memory operations diagrammed in FIG. 7. Firstin step 1002, a read request for data stored in a second memory bank isreceived from a second one of the plurality of serial data linkinterfaces. In step 1004, a serial data link interface status indicatorcorresponding to the second data link interface is updated to indicatethat the second serial data link interface is being utilized. A memorybank status indicator corresponding to the second memory bank identifieris updated to indicate that the second memory bank is being utilized instep 1006. Finally, in step 1008 data is routed between the secondmemory bank and the second serial data link interface. One or more ofthe steps shown in FIG. 10 may be performed concurrently.

Returning to FIG. 1B, the memory device shown includes a single datalink interface 120 configuration that uses a virtual multiple link. FIG.1B can be implemented with the configuration of the input serial toparallel register 232 that has been previously described. Moregenerally, the embodiment of FIG. 1B can be implemented with the memorydevice 200, but with only one of the two serial data links being used.In conventional flash memory, I/O pins are occupied until an operationis complete. Therefore, no operation can be asserted during device busystatus, which reduces device availability and decreases overallperformance. In the example depicted in FIG. 1B, any available memorybank checked by a “read status” operation can be accessed after anoperation has been initiated in one of the two memory banks.Subsequently, the memory device can utilize the serial data link toaccess available memory banks through the supplemental switch circuit.Therefore, in accordance with this aspect of the invention, a singlelink may be used to access multiple memory banks. This virtual multiplelink configuration emulates multiple link operations using a singlelink.

FIG. 12 illustrates a timing diagram of a memory device with two memorybanks performing memory operations using a virtual multiple linkconfiguration in which a “page program” in bank 0 and a “page read” inbank 1 are to be executed. First, a “page program” command 1202 directedat memory bank 0 is issued. The “page program” command has already beendescribed earlier, but to recap, the “serial data input” command isfirst performed to load into the bank 0 page register the data to beprogrammed to bank 0. Subsequently, a “page program command is issuedand the data is written from the page register into bank 0. When a “readstatus” command 1204 is issued device, the device indicates 1206 thatbank 1 is “ready” (and that bank 0 is “busy”). Consequently, based onthe virtual multiple link configuration in accordance with theinvention, a “page read” command 1208 directed at memory bank 1 can beand is issued while memory bank 0 is busy. The “page read” command hasbeen previously described. A “read status” command 1210 can be (and inFIG. 12 is shown to be) issued to determine the status of the memorybanks. The result of the “read status” command indicates during interval1212 that both memory bank 0 and memory bank 1 are ready. Finally, a“page read” command 1214 (for bank 1) is issued that results in thecontents of the memory address corresponding to the bank 1 “page read”command to be outputted on the serial output pin (SOP). Note that whilethe “page program” operation on bank 0 is taking place, the serial datainterface link pin SIP is available to receive the “read status” commandwhich identifies bank 1 as “ready”. Similarly, once the “page read”command on bank 1 has been initiated, the SIP pin is again available fora “read status” command, indicating that both banks 0 and 1 are nowready. As a result, the single serial data interface link can be used toaccess and check the status of both banks. Aspects of the virtualmultiple link feature implemented in FIG. 12 illustrate that the link isavailable even while an earlier memory operation is pending. At leastone benefit arising from this feature is the reduced pin count resultingfrom the virtual multiple link configuration. Another benefit is theincreased performance of the memory device.

In addition, when aspects of the virtual multiple link feature areimplemented with memory devices with dual or quad-link configurations,it may be desirable to consider all but one of the links as beinginactive. For example, three of the four links in a quad-linkconfiguration (in FIG. 1C) may not be used and may be designated as NC(no connection). At least one benefit of such an implementation is areduction in the number of pins on the memory device while maintaininglink flexibility and availability.

In accordance with various aspects of the invention, FIG. 13 illustratesa daisy-chain cascade configuration 1300 for serially connectingmultiple memory devices 200. In particular, Device 0 is comprised of aplurality of data input ports (SIP0, SIP1), a plurality of data outputports (SOP0, SOP1), a plurality of control input ports (IPE0, IPE1), anda plurality of control output ports (OPE0, OPE1). These data and controlsignals are sent to the memory device 1300 from an external source(e.g., memory controller (not shown)). Moreover, in accordance with theinvention, a second flash memory device (Device 1) may be comprised ofthe same types of ports as Device 0. Device 1 may be serially connectedto Device 0. For example, Device 1 can receive data and control signalsfrom Device 0. One or more additional devices may also be seriallyconnected alongside Device 0 and Device 1 in a similar manner. The finaldevice (e.g., Device 3) in the cascade configuration provides data andcontrol signals back to the memory controller after a predeterminedlatency. Each memory device 200 (e.g., device 0, 1, 2, 3) outputs anecho (IPEQ0, IPEQ1, OPEQ0, OPEQ1) of IPE0, IPE1, OPE0, and OPE1 (i.e.,control output ports) to the subsequent device. The previously describedcircuits in FIG. 2B illustrate how the signals can be passed from onedevice to a subsequent daisy chained device. In addition, a single clocksignal is communicated to each of the plurality of serially connectedmemory devices.

In the aforementioned cascade configuration, device operations of thecascaded memory device 1300 are the same as in a non-cascaded memorydevice 200. One skilled in the art will recognize that the overalllatency of the memory device 1300 may be increased in a cascadeconfiguration. For example, FIG. 14 depicts a highly-simplified timingdiagram for a “page read” memory command 1402 received at memory device1300 and directed at a memory bank in Device 2 in memory device 1300.The memory command is received at memory device 1300 and sent throughDevice 0 and Device 1 to Device 2. For example, the data streamcorresponding to the “page read” command 1402 will be transferred fromthe SIP0 line of Device 0 in memory device 1300 through the circuitry ofDevice 0 and outputted at the SOP0 line of Device 0. The output ofDevice 0 is reflected in the simplified timing diagram in FIG. 14 on theSOPx_D0 output line at 1404. “SOPx_D0” corresponds to serial output port0 on Device 0. Similarly, the data stream is subsequently received atSIPx_D1 on Device 1 (at 1406) and sent through Device 1 to be outputtedby Device 1 on the SOPx_D1 line at 1408. Next, the data stream isreceived at SIPx_D2 on Device 2 at 1410. In this example, since the“page read” command is directed to a memory bank in Device 2, in amanner similar to that described for the circuitry in memory device 200,the circuitry in Device 2 receives the “page read” command and controlsthe transfer of the requested data from a memory bank in Device 2 to theSOPx_D2 output line on Device 2 at 1412. The data outputted by Device 2is received at Device 3 at 1414 and transferred through Device 3 andoutputted from memory device 1300. One skilled in the art will recognizefrom the simplified timing diagram of FIG. 14 that a predeterminedlatency of four clock cycles resulted due to the cascadingconfiguration.

Meanwhile, the cascade configuration allows a virtually unlimited numberof devices to be connected without sacrificing device throughput.Aspects of the invention may be beneficial in the implementation ofmulti-chip package solutions and solid state mass storage applications.The incoming data stream in a cascaded device 1300 is similar to that ofa non-cascaded memory device 200, however, the first byte of the datastream may be preceded by a one-byte device identifier. For example, avalue of “0000” in the first byte may indicate Device 0, while a valueof “0001” may indicate Device 1. One skilled in the art will understandthat the device identifier need not necessarily be limited to one byte,but may be increased or decreased as desired. Also, the deviceidentifier need not necessarily be positioned as the first byte in adata stream. For example, the size of the identifier may be increased toaccommodate more devices in a cascaded configuration and be positionedwith the address field of the data stream.

In one embodiment in accordance with the invention, the memory device200 uses a single monolithic 4 Gb chip. In another embodiment, thememory device uses a pair of stacked chips for 8 Gb. In yet anotherembodiment, the memory device 1300 uses a stack of four chips to make up16 Gb. A flash memory device in accordance with various aspects of theinvention may be an improved solution for large nonvolatile storageapplications such as solid state file storage and other portableapplications desiring non-volatility. The memory device 1300 may benefitfrom a novel flash device cascade scheme for virtually unlimited numberof linked devices to accommodate system integration with greaterexpandability and flexibility. The serial interface will provideadditional performance improvement with higher clock rate, better signalintegrity and lower power consumption. The serial interface alsoprovides unlimited expandable I/O width without changing packageconfiguration. Furthermore, the one-side pad architecture of a memorydevice in accordance with the invention, with fewer number of I/O,greatly reduces chip package size.

As stated earlier, the memory devices can be dual-bank memories, whereeach bank can be accessed by any serial link. The serial interface ofthe memory device greatly improves data throughput over traditionalparallel interface schemes, while supporting feature-rich operations.For example, a program operation can be performed in 200 μs on a (2K+64) byte page and an erase operation can be performed in 1.5 ms on a(128K+4K) byte block. An on-chip write controller may be used toautomate all program and erase functions including pulse repetition,where used, and internal verification and margining of data. Inwrite-intensive systems, ECC (Error Correcting Code) with real timemapping-out algorithm may be used to enhance the extended reliability of100K program/erase cycles in the memory device.

The usefulness of the various aspects of the invention should beapparent to one skilled in the art. The use of any and all examples orexemplary language herein (e.g., “such as”) is intended merely to betterilluminate the invention and does not pose a limitation on the scope ofthe invention unless otherwise claimed. No language in the specificationshould be construed as indicating any non-claimed element as essentialto the practice of the invention.

The present invention has sometimes been described in terms of preferredand illustrative embodiments thereof. Numerous other embodiments,modifications and variations within the scope and spirit of the appendedclaims will occur to persons of ordinary skill in the art from a reviewof this disclosure.

1. A memory device comprising: flash memory; read circuitry configuredto obtain read data from said flash memory to facilitate subsequenttransmission of the read data; an output buffer configured to receivethe read data and to transmit the read data through an output port inresponse to an output enable signal, the output enable signal being heldat a logic level for a period of time that delineates a length of saiddata transmitted from said output port; a clock input configured toreceive a clock signal having edges; and additional circuitry configuredto clock out the read data from said output port in tandem with saidedges for a duration of time corresponding to the period of time theoutput enable signal is held at the logic level.
 2. The memory device asin claim 1, wherein the output buffer transmits the read data throughthe output port at a predetermined delay after the output enable signalis driven to the logic level.
 3. The memory device as in claim 1 furthercomprising: a first input port configured to receive commandinformation; and a second input port configured to receive an inputenable signal that indicates a beginning of a command data stream thatcontains said command information by way of a transition from aninactive state to the active state.
 4. The memory device as in claim 3,wherein said command data stream includes a serial data stream.
 5. Thememory device as in claim 1, wherein said read data includes a serialdata stream.
 6. A memory device comprising: flash memory; read circuitryconfigured to obtain read data from said flash memory to facilitatesubsequent transmission of the read data; an output buffer configured toreceive the read data and to transmit the read data through an outputport in response to an output enable signal, said read data transmittedfrom said output port including a first data stream and a second datastream, the first data stream being delineated from the second datastream based on a logic level of said output enable signal, the outputenable signal being held at a logic level for a period of time thatdelineates a length of the first data stream and the second data streamtransmitted from said output port.
 7. The memory device as in claim 6further comprising: a first input port configured to receive commandinformation; and a second input port configured to receive an inputenable signal that indicates a beginning of a command data stream thatcontains said command information by way of a transition from aninactive state to the active state.
 8. The memory device as in claim 7,wherein said command data stream includes a serial data stream.
 9. Thememory device as in claim 6, wherein said read data includes a serialdata stream.
 10. The memory device as in claim 6, wherein the outputbuffer transmits the read data through the output port at apredetermined delay after the output enable signal is driven to thelogic level.
 11. A method for providing a data stream comprising:driving an output enable signal to an active state for a period of time,the period of time substantially corresponding to a number of bits ofdata to sequentially appear at an output port of a flash memory device,the number of bits being up to a page buffer in size; transmitting thenumber of bits of data from the output port for the period of time;receiving a free-running clock having inactive to active and active toinactive transitions; and transmitting one bit of the data from theoutput port on each of the inactive to active transitions of thefree-running clock during the period of time.
 12. The method as in claim11 further comprising: receiving an input enable signal transitioningfrom an inactive state to the active state that indicates a beginning ofa command data stream that contains command information; and receivingsaid command data stream.
 13. The method as in claim 12, wherein thecommand information includes a read command.
 14. The method as in claim12, wherein the command information includes a read address.
 15. Themethod as in claim 12, wherein bits of the command data stream arereceived on each of the inactive to active transitions of the freerunning clock while the input enable signal is in the active state. 16.A method for providing a data stream comprising: driving an outputenable signal to an active state for a period of time, the period oftime substantially corresponding to a number of bits of data tosequentially appear at an output port of a flash memory device, thenumber of bits being up to a page buffer in size; transmitting thenumber of bits of data from the output port for the period of time wherea first bit of the data is provided within a first clock period whilethe output enable signal is driven to the active state within the firstclock period, and a last bit of the data is provided within a secondclock period while the output enable signal is driven to an inactivestate within the second clock period.
 17. The method as in claim 16further comprising: receiving an input enable signal transitioning froman inactive state to the active state that indicates a beginning of acommand data stream that contains command information; and receivingsaid command data stream.
 18. The method as in claim 17, wherein thecommand information includes a read command.
 19. The method as in claim17, wherein the command information includes a read address.
 20. Themethod as in claim 17, wherein bits of the command data stream arereceived on each inactive to active transition of a clock while theinput enable signal is in the active state.
 21. A memory systemcomprising: a controller; and a number of memory devices, each of thememory devices including flash memory; a clock input configured toreceive a clock signal having edges, read circuitry configured to obtainread data from said flash memory to facilitate subsequent transmissionof the read data; an output buffer configured to receive the read dataand to transmit the read data through an output port in response to anoutput enable signal, the output enable signal being held at a logiclevel for a period of time that delineates a length of said read datatransmitted from said output port; and additional circuitry configuredto clock out the read data from said output buffer in tandem with saidedges for a duration of time corresponding to the period of time theoutput enable signal is held at the logic level.
 22. The memory systemdevice as in claim 21 wherein each of said memory devices furtherincludes a first input port configured to receive command information,and a second input port configured to receive an input enable signalthat indicates a beginning of a command data stream that contains saidcommand information by way of a transition from an inactive state to anactive state.
 23. The memory system as in claim 21, wherein the outputbuffer transmits the read data through the output port at apredetermined delay after the output enable signal is driven to thelogic level.
 24. A method for providing a data stream comprising:driving an output enable signal to an active state for a period of time,the period of time substantially corresponding to a number of bits ofdata to sequentially appear at an output port of a flash memory device,the number of bits being up to a page buffer in size; and transmittingthe number of bits of data from the output port for the period of time,a first bit of the data is provided at a first predetermined delay afterthe output enable signal is driven to the active state, and a last bitof the data is provided at a second predetermined delay after the outputenable signal is driven to an inactive state.
 25. The method as in claim24 further comprising: receiving an input enable signal transitioningfrom an inactive state to the active state that indicates a beginning ofa command data stream that contains command information; and receivingsaid command data stream.
 26. The method as in claim 25, wherein thecommand information includes a read command.
 27. The method as in claim25, wherein the command information includes a read address.
 28. Themethod as in claim 25, wherein bits of the command data stream arereceived on each inactive to active transition of a clock while theinput enable signal is in the active state.